About 15% of new Conservative and Labour MPs came from lobbying backgrounds according to research by an anti-spin campaigning group which is calling on Nick Clegg to urgently introduce a promised new register of lobbyists.

Spinwatch said the figures – 19 out of 143 Tories and 11 out of 67 new Labour MPs – suggested there was a "revolving door" between parliament and the industry attempting to influence it. The register was crucial to bring some transparency to the system. The coalition government said it is committed to publishing the register.

David Miller, a spokesman for Spinwatch, which was set up in the aftermath of the Iraq war and is funded through donations, said: "When people move between being lobbyists to being MPs and ministers, there is a potential conflict of interest. There's a cooling off period when they leave – but that's not statutory. There should be a cooling off period beforehand as well.

"Given that Cameron was in PR and Clegg was a professional lobbyist, the question is whether businesses have special access as the result of those relationships?"

In the Conservative party George Eustice, formerly associate director at Portland PR and Cameron's former spokesman, is MP for Camborne and Redruth. His former colleague at Portland, Charlotte Leslie, took Bristol North West.

Priti Patel, former director at Weber Shandwick, became MP for Witham; Damian Collins came from Lexington Communications to take Folkestone and Hythe; and Penny Mordaunt, former associate at Hanover took Portsmouth North.

On the Labour benches, Emma Reynolds, a senior consultant at Cogitamus is now MP for Wolverhampton North East and Thomas Docherty, account director at PPS Group is MP for Dunfermline and West Fife. There are no new Liberal Democrat MPs with lobbying backgrounds.

On Wednesday evening, Number 10 confirmed that Clegg would assume responsibility for the register as well as other elements designed to clean-up the political system including party donations and the Independent Parliamentary Safeguarding Authority, responsible for policing MPs' expenses.

The government is also poised to publish a full list of special advisers appointed since the election after promising to cut the number of spin-doctors on the public pay-roll under Labour.

A Conservative spokesman said: "As the coalition agreement sets out, the government is committed to regulating lobbying through introducing a statutory register and ensuring greater transparency."